In pseudoscience literature one frequently encounters the claim that there are some people, called "sensitives" or "psychics," who somehow can pick up the thoughts of others and even transmit their own thoughts to people who are not "sensitives." This direct mind-to-mind communication is sometimes claimed to be instantaneous and independent of distance. It is also often claimed that all people — and even domestic animals such as cats, dogs, and horses — possess this ability to some degree, and that ordinary coincidences are in fact not ordinary, but rather mysterious demonstrations of this supposed ability. (For example, one suddenly thinks of Uncle Charlie for the first time in years, and then later learns that Uncle Charlie was in a serious accident at about the time he mysteriously sprang to mind.) All such pseudoscientific discussions of ESP or telepathy also claim that it is "proven beyond a doubt" that ESP or telepathy exists.

The "proof" quoted is usually of an anecdotal variety — that is, a large collection of unverifiable stories like the "Uncle Charlie" story above. Sometimes, however, it is claimed that "scientific tests" at respected" research institutions have conclusively demonstrated that ESP exists; or "government tests" have proved it; or, that the Russians are "working hard" on it; or, that the CIA uses it; etc., etc. Sometimes, but rarely, specific experiments are cited as having confirmed the existence of telepathy, clairvoyance, precognition, telekinesis, or other such "supernatural" abilities in humans or animals.

Serious questions can be raised concerning all the claims listed above. First, it is the essentially unanimous opinion of psychologists that the existence of ESP has not been shown in any experiment conducted to date. In fact, all procedurally valid and reproducible experiments have failed to demonstrate the existence of any non-sensory channel for information; in experiments where fraud and trickery are ruled out by tight controls, no "extrasensory" abilities are ever demonstrated, even by world-famous "psychics." (See the first three references below for detailed reviews of the best-known experiments.)

It is also important to realize that the existence of an ESP ability in humans or other animals would not be consistent with anything we know about nature, either from the standpoint of physics or from the standpoint of physiology. Let us consider the physiological aspect first.

All of the "higher" animals show the same fundamental organization of their sensory systems. The specialized cells (neurons) that form the central nervous system (CNS) of man and other higher animals are themselves insensitive to sensory stimuli. For each kind of important stimulus in the environment, animals have evolved highly specialized sensory organs. Each such sense organ contains unique, highly adapted cells that are sometimes called "transducers." Each stimulus in the environment involves a special kind of cellular activity. Vision involves direct detection of particles of light (photons). Hearing involves direct detection of organized, wave motion of air molecules. Smell and taste involve direct detection of molecular shapes. Sensory organs (eyes, ears, nose) support the cells that are specialized to detect photons, molecular motion, and molecular shapes directly. These cells generate impulses that travel along nerve fibers and which are then processed in intermediate switching and coding areas, finally reaching the brain in a form that can be interpreted by brain cells.

The point is that the brain itself is insensitive to sensory information. If one opened a skull and exposed the living brain to light, sound, heat, smells, etc., the brain would be totally unaware of the application of these stimuli directly to its tissues. For obvious reasons, the sensory organs containing the transducer cells are located at or near the surface of the body in all animals, including humans. When we apply this universal rule of nature concerning information input to the brain to claims for telepathy, we come up short on all accounts. Assume that some kind of "something" is radiated from a person’s brain as he or she thinks. How would another person’s brain ever know about it? Nowhere on the surface of the body is there a specialized organ that appears to lack a function and which contains transducer cells sensitive to "unknown forces." Nor, contrary to popular myth, is there any large area of the brain whose function is unknown and which might be responsible for reception and interpretation of signals from the hypothetical ESP organ.

Furthermore, in the course of evolution many kinds of animals have developed extremely acute senses of one kind or another, compared to those of humans. Dogs have much more highly developed sense of smell than do humans; hawks and eagles, more acute eyesight, bats, much wider range of hearing; etc. Where is the animal that has a much more highly developed ESP-sense than humans? In fact, the ability to sense the presence of predatory animals that could not be seen, heard, or smelled would confer such enormous advantages of its possessors that evolution should have made ESP as common as fur, claws, and moist noses. It has not happened. Could it be that no such sense organ exists because there is n o stimulus for the organ to detect?

Some persons argue that only human beings are capable of ESP communication; or, that only certain, special persons are so endowed. Comparative anatomy fails to show any evidence of either contention.

A proponent of ESP could argue that telepathy differs from all other senses in that the brain itself is the telepathic sense organ. In this case the detected stimulus would require the penetrating power of X-rays or nuclear radioactivity in order to get through the skull to reach the brain! This brings us to the realm of physics, where ESP falls down as badly as in the realm of physiology.

Physicists have found, in 400 years of searching nature ever more closely and at an increasingly fundamental level, evidence for the existence of only four fundamental forces in nature. These are gravity, the electromagnetic force, and the weak and strong nuclear forces. Because these four forces are very well understood, and the theories which describe them have been so thoroughly tested, it is known that NONE of these forces could be responsible for the hypothetical ESP stimulus. What then about a new force, previously unknown to science? An undiscovered force which can act in the everyday environment strongly enough to account for alleged ESP phenomena is essentially certain not to exist, for precisely the same reason you can be certain there is not an elephant in the room with you as you sit reading this! There is no place for it to be, no place for it to hide. If such a force existed, everything would be different than we see it to be, because the force would affect everything in some way. Forces are universal, exerted from subatomic particle to subatomic particle, felt equally by planets, rocks, molecules and tomcats, because all matter is made of the same basic triad of particles: electrons, protons, and neutrons, at one level; electrons, up quarks an down quarks at the next level down. To argue that such a force exists but has no observable effects is contradictory; we know of the existence of forces only through their effects. Furthermore, all known interactions in physics diminish at least as fast as the inverse square of the distance, and often far faster than that. All interactions propagate from point to point in space-time at a speed at or below the speed of light. ESP is said to violate these universal rules for all forces in nature.

This brings us to the most important point of all, and one essentially never considered by proponents of ESP. We know that electromagnetic radiation, for instance, exists over a vast range of frequencies or wavelengths that we are totally blind to, because we have no sensory organs that will respond to such radiation. Our knowledge of the existence of such radiation does not depend on the accidental birth of mutants or supermen or "sensitives" who can somehow detect radio or ultraviolet rays directly. Nobody can detect such waves directly; the question is irrelevant because we are dealing with a real phenomenon of nature, which is universal in character. There are a vast number of sources in nature for electromagnetic radiation in any part of the spectrum it is desired to study; and it is simple to construct artificial sources of electromagnetic radiation, as intense and monochromatic as we wish. It is equally easy to construct detectors for such radiation, again as sensitive and broadly responsive as we wish them to be. Even when using the part of the electromagnetic spectrum that humans can sense directly, the visible spectrum, one would prefer to use instruments such as movie and TV and still cameras so as to have a permanent, objective record, unaffected by fatigue, bias, defects of vision, and poor memory that would afflict a human detector-describer-recorder. In other words, when one is dealing with a real process, one studies the process directly. If ESP existed, the question of whether or not humans had ESP would be totally irrelevant; the "radiation" or whatever other physical interaction is involved could be best studied directly.

It has been pointed out over and over, most forcefully by Joseph Jastrow and John Mulholland in 1938, and by George R. Price in 1955, that the ESP experiments that are done are actually irrelevant to whether ESP exists or not! What is usually done is a "guessing" experiment, for example a game of guessing playing cards or symbol cards. Any amateur magician who is knowledgeable, or any gambler who is effective, can score high in such games using nothing but subtly disguised sensory perception. Over and over, one hears of high scores in such games being "evidence" of ESP. But a machine which randomly chose cards by some automatic process would also obtain a high score on occasion. We would hardly say the machine had ESP, and it isn’t using trickery, either! Where experiments have tight procedural controls to rule out cheating and trickery, and where the runs are long enough to average out the chance fluctuations toward very high and very low scores, the "guesses," either human or mechanical, are precisely in accord with chance expectations.

Two characteristics exhibited by all pseudosciences are that no physical process is ever actually discovered or studied, and that "research" does not progress but rather remains perpetually inconclusive. The ESP experiments conducted by pseudoscientists fit this pattern perfectly.

In summary, the existence of ESP has not been demonstrated in either everyday life or the laboratory. Furthermore, the faulty claims for ESP run counter to well-established, well-tested laws of nature. To be consistent wit the rules by which reality is regulated, ESP would require elaborate, highly specialized organs for sending and receiving ESP radiation — organs that are not evident. The ESP radiation should be detectable directly and capable of study by sensitive instruments. Such instruments do not exist because such radiation does not exist in any recognizable form.